There is a demand for improving the quality of displayed images, as by improving signal processing techniques and driving techniques for image display devices.
In general, the image quality of an image can be improved by increasing the resolution of the image and smoothing the texture thereof. The amount of information of an image is expressed in the unit of pixels indicative of dots (dots) which constitute the image. The number of pixels of an image is expressed by the number of horizontal and vertical dots of the image, such as 800×600 or 1024×768. More specifically, the greater the number of pixels (dots), the more smooth the texture of the image and the more the amount of information constituting the image.
To display an image with high resolution, there is a technique (refer to Patent Document 1, for example) which makes it possible to display an image with twice as high resolution in a multi mode compared to a system using only one display, by using, for example, two displays 1 and 2 so as to cause the display 1 to display an image in a normal single mode and so as to cause the respective displays 1 and 2 to display the left and right halves of the image in the multi mode.    [Patent Document 1] Japanese Patent Application Publication No. Hei-10-124024
If an image is displayed with increased resolution, the amount of information constituting the image increases, so that the amount of data to be transferred to the display 1 or 2 increases and the data transfer rate needs to be increased. For this reason, this system is constructed to perform transfer of image data without increasing the data transfer rate, by reducing the amount of data for each dot of the displays 1 and 2 and performing conversion of the reduced data through signal processing.
In addition, the image quality of a moving image in particular can be improved by increasing a frame rate which is the number of times per second of updating of a screen.
For example, when a moving image is to be projected and displayed on a screen by using a projector, the projector displays a frame image line by line by performing horizontal scan on a line by line basis, and after having scanned all lines of one frame of image, starts scanning image data of the succeeding frame, thereby displaying the moving image.